Detonator assembly

ABSTRACT

A detonator assembly which includes first and second cable coils, a detonator which is connected to one end of the first cable coil, a first connector which connects an opposing end of the first cable coil to one end of the second cable coil, a second connector which is connected to an opposing end of the second cable coil, and confinement structure around the first and second cable coils.

BACKGROUND OF THE INVENTION

This invention relates generally to a detonator assembly and is alsoconcerned with a method of installing a plurality of detonators in aplurality of respective boreholes.

It is known to make use of electronic detonators, which are individuallyprogrammable, to establish a blasting configuration. Each detonator isassigned a unique identity number and is connected in parallel to atrunk cable. As each detonator is uniquely identified it is possible toaddress a chosen detonator and program desired blasting information intothe detonator.

In a different connection technique a plurality of detonators areconnected to one another in a daisy-chain configuration. In thisarrangement the detonators are addressed in sequence with a givendetonator being placed in a programming mode while the other detonatorsare in a non-programmable mode. Certain benefits are associated with adaisy-chain arrangement although one disadvantage arises from the needto make a connection between each detonator in the sequence and thefollowing and preceding detonators. This aspect and the capability ofbeing able to insert a detonator to a variable depth inside a borehole,give rise to a requirement that two variable lengths of cable must beassociated with each detonator viz. a first cable length to go down afirst borehole and a second cable length to go from the first boreholeto an adjacent, second borehole. In dealing with the cables associatedwith each of a large number of detonators, the cables can becomeentangled with one another and errors can arise in configuring ablasting sequence.

Another aspect which should be addressed is that each detonator shouldbe packaged in a way which facilitates the use of automatedmanufacturing and testing processes, which readily allows for handlingand transport, and which enables each detonator to be labelled so thatit complies with applicable regulations and legislation.

SUMMARY OF INVENTION

The invention provides a detonator assembly which includes a first cablecoil with first and second ends, a second cable coil with third andfourth ends, a detonator connected to the first end of the first cablecoil, a first connector connected to the second end of the first cablecoil and to the third end of the second cable coil, and a secondconnector connected to the fourth end of the second cable coil andwherein a first variable length of cable, extending from the first end,can be drawn from the first cable coil without materially moving thefirst connector and a second variable length of cable, extending fromthe fourth end, can be drawn from the second cable coil withoutmaterially moving the first connector.

The first cable coil may be provided in the form of a first tubularroll. The first end may be inside the first tubular roll. Similarly thesecond cable coil may be provided in the form of a second tubular rolland the fourth end may be inside the second tubular roll.

The detonator assembly may include a confinement structure of anyappropriate type for maintaining the cable in the required coiledconfiguration.

The first connector may be accessible without opening or removing theconfinement structure. The first connector may for example be positionedon an outer side of the confinement structure.

The second and third ends of the cables, which are connected to thefirst connector, are preferably integrally connected and at no time areseparable from each other. These ends may extend out of the confinementstructure.

The confinement structure may be in the form of a housing which includesa first compartment for the first cable coil. A second compartment maybe provided inside the housing for the second cable coil. At least onedivider may be positioned between the compartments. Preferably the firstand second cable coils are separated by at least two dividers. Eachdivider may be provided in any appropriate way and preferably eachdivider abuts at least one recessed formation which extends from anouter surface of the housing into an interior of the housing.

The confinement structure may be circular cylindrical or in the form ofa parallelepiped. In one embodiment the confinement structure is in theform of a housing which is made from a relatively rigid material, andthe housing has four relative large sides and two relatively small sideswhich form opposed ends of the housing.

The housing may be made from any suitable material and maybe made from arigid material such as cardboard which may be corrugated or a similarbio-degradable material.

The first and third ends of the cables may extend through respectiveapertures in the smaller sides of the housing.

In a preferred form of the invention the confinement structure is madefrom flexible sheet material. The sheet material may extend around thecable coils and may have a composition which allows the sheet materialto be shrunk onto the coils. This type of sheet material is known in theart.

Each cable coil may be positioned inside a respective enclosure which,in turn, is located inside the confinement structure. The enclosure maycomprise flexible sheet material such as plastic film. Each cable coilmay comprise a plurality of windings arranged in overlying layers arounda hollow core.

The windings may be arranged so that they form a circular cylindricalshape. The first end may extend from an innermost winding of the firstcable coil, facing the respective hollow core. This allows the cable tobe withdrawn from the first cable coil without removing the first coilfrom the confinement structure.

The fourth end may be similarly configured with respect to the secondcable coil.

The invention also provides a method of forming a cable coil assemblywhich includes the steps of drawing cable from a supply source andwinding a single coil of a first predetermined length around a firstformer, severing the cable so that the single coil is separated at afirst end from the supply source, and forming a first cable coil bywinding cable, of a second predetermined length which is shorter thanthe first length, drawn from the single coil, commencing at the firstend, around a second former, and thereby simultaneously forming a secondcable coil of a length which is substantially equal to the differencebetween the first and second lengths.

The single coil may be formed by winding the cable in a first directionaround the first former and the first coil may be formed by windingcable drawn from the single coil in a second direction around the secondformer, wherein the first direction is opposite to the second direction.

The first cable coil may be positioned so that it is co-axial with thesecond cable coil.

The invention also provides a method of installing a plurality ofdetonators in a respective plurality of boreholes in a daisy-chainconfiguration which includes the steps, for each borehole, of drawing afirst length of cable from a first cable coil in confinement structure,positioning a first detonator which is connected to a first end of thefirst length of cable at a predetermined depth inside the respectiveborehole, drawing a second length of cable from a second cable coilinside the confinement structure and connecting a first connector whichis at a junction of the first and second coils, at the confinementstructure, to a second connector which is at an end of a respectivesecond length of cable associated with a first borehole.

The method may include the step of connecting a respective secondconnector at an end of the second length of cable, associated with therespective borehole, to a respective first connector at a secondborehole.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further described by way of examples with reference tothe accompanying drawings in which:

FIG. 1 schematically depicts a plurality of detonators which are locatedin respective boreholes and which are connected to each other in adaisy-chain configuration;

FIG. 2 is a cross sectional view of a detonator assembly according tothe invention;

FIGS. 3 and 4 are perspective views of the detonator assembly of FIG. 2illustrating different aspects thereof;

FIG. 5 is a schematic side view of a detonator assembly according to theinvention with a housing thereof fully opened;

FIGS. 6 to 8 show the detonator assembly in different stages ofmanufacture;

FIGS. 9, 10 and 11 illustrate steps in the winding of cable coils foruse in a detonator assembly according to one form of the invention;

FIG. 12 is a perspective view of a detonator assembly according to avariation of the invention;

FIG. 13 is a side view in cross section of the detonator assembly inFIG. 12; and

FIG. 14 is similar to FIG. 1, depicting the use of a plurality of thedetonator assemblies in FIG. 12, in a blasting system.

DESCRIPTION OF PREFERRED EMBODIMENT

FIG. 1 of the accompanying drawings illustrates schematically aplurality of boreholes 10A, 10B . . . 10N which are drilled in theground 12 using conventional techniques. A respective detonator 14A, 14B. . . 14N is placed in each borehole. A first length 16A, 16B . . . 16Nof cable extends from the respective detonator to a respective firstconnector 18A, 18B . . . 18N which is positioned at surface, and arespective second length 20A, 20B . . . 20N of cable extends betweenadjacent pairs of connectors 18A and 18B, 18B and 18C, . . . 18N-1 and18N.

As indicated in the preamble to this specification practical problemsarise, when making a daisy-chain arrangement of the type shown in FIG.1, in that the lengths 16 and 20 of the cables are variable. If standardlengths of cable are connected, beforehand, to a connector 18 then oncea detonator 14 is placed in a borehole a first excess portion of cablecan lie at the mouth of the borehole while, once a connection is madebetween a connector 18A and a following connector 18B, a second excesslength of cable can lie on the surface between the boreholes. Theinvention is aimed at addressing at least this type of problem.

FIG. 2 illustrates a detonator assembly 30 according to the invention.The assembly includes a cable confinement structure which is formed by ahousing 32 which is of parallelepiped form which, as is more clearlyshown in FIGS. 3 and 4, has four relatively large rectangular sides andopposed ends 34 and 36 which are smaller than the larger rectangularsides. The housing 32 is made from a corrugated cardboard blank 38generally of the type shown in FIG. 5 which is formed with lines ofweakness and cut-outs so that the blank can be folded into theconfiguration shown in FIGS. 3 and 4. At three of its longitudinalcorners 40A, 40B and 40C respectively, portions of the blank can beforced inwardly to form right angled recess formations 42A, 42B and 42Crespectively. As is shown in FIG. 2 end portions 44 and 46 of the blankabut these formations, on an inner side of the housing, and therebydivide the housing interior into three compartments 50, 52 and 54respectively.

FIG. 4 illustrates further details of the recessed formation 42C whichextends a substantial portion of the width of the respective side,designated 56. A relatively large rectangular window 58 is formed in abase of the recessed formation. A rectangular cardboard insert 60, whichhas a centrally located relatively small rectangular window 62, islocatable in the recessed formation 42C.

FIGS. 9 to 11 illustrate successive stages in the manufacture of twocoils of cable from a single length of cable 66. A large drum 68 of thecable 66 is mounted to suitable support structure 70. The cable 66 ispassed over suitable pulleys and rollers 72 and 74 respectively and iswound in a first direction 76 about a first former 78. A predeterminedlength of cable, say 40 metres long, is wound onto the former 78 to forma single coil 80. A first end 82 of the cable is positioned inside aninterior of the coil. Thereafter the coil is severed by means of a setof knives 84. The cable is then wound onto a second former 86 in adirection 88 which is opposite to the first direction 76. The cable isdrawn from the single coil 80 for this purpose. In this way, as is shownin FIG. 11, a first coil 90 is formed with a predetermined length ofcable of, say, 30 metres and a second coil 92 is formed with apredetermined length of, say, 10 metres. The first coil has a second end94 which is integrally connected to an end 96 of the second coil(referred to herein as the third end). A free end of the coil 92designated 98, and referred to herein as the fourth end, is positionedinside an interior of the second coil.

As is shown in FIG. 2 the first and second coils, which are coaxiallyaligned, are inserted into the compartments 50 and 54 respectively. Theend portions 44 and 46, which act as dividers, have slits 99 throughwhich parts of the cable section 100 between the coils (effectively theintegrally joined ends 94 and 96 shown in FIG. 11) can pass. The cablesection 100 is then looped through the window 58, as is shown in FIGS. 4and 5. The first end 82 of the first coil is passed through an aperture104 in the end 34 of the housing while the fourth end 98 of the secondcoil is passed through an aperture 106 in the end 36.

Referring particularly to FIGS. 7 and 8 a first connector 110 is crimpedonto the cable section 100 without severing this cable i.e. the firstand second coils are at all times integrally connected to each other. Alabel 112 is attached to the cable adjacent the first connector. Asecond connector 114 is attached to the fourth end of the cable. Adetonator 116 of conventional design which is suited for daisy-chainconnections is attached to the first end 82 of the cable.

The end 82 is looped, as is shown in FIGS. 2 and 8, and the detonator116 is inserted into the compartment 50 so that it lies inside thehollow interior of the first coil 90. The fourth end 98 is folded overan external surface of the housing and is coupled with a press fit tothe first connector 110. The cardboard insert 60 is then manipulated sothat the connectors 110 and 114 pass through the window 62 together withthe label 112. The insert is then pushed into the recessed formation 42C(see FIG. 4) so that the connectors are contained within the recessedformation. Thereafter a preformed tubular sleeve 120, of rectangularcross-section, is placed over the housing to envelope the four largersides. The sleeve is pre-printed with information which relates to thedetonator and which is prescribed by regulation and legislation. Thesleeve has slits 122 which define a rectangular section 124 which can befolded inwardly to nestle in the recessed formation 42B so that thesleeve is thereby kept in position on the housing.

When the detonator assembly is to be used it is transported to a blastsite and allocated to a particular borehole 10. A tab 136 on the sleeveis pulled to tear the sleeve free from the housing or, alternatively,the sleeve is torn only enough to expose the connector set. Theconnectors 110 and 114 are then detached from each other. The detonator116 is extricated from the interior of the housing. Cable is drawn fromthe first coil 90 so that the detonator can be inserted to apredetermined depth inside the borehole. It is pointed out in thisrespect that the detonator 116 shown in FIG. 7 corresponds to adetonator 14 shown in FIG. 1. The length of cable between the detonatorand the housing 32 is designated by the reference numeral 16 in FIG. 1.A predetermined length of cable, corresponding to the length 20 shown inFIG. 1, is drawn from the second coil. This enables the connector 114 tobe connected to a corresponding first connector 110 at an adjacentborehole 14B, as is shown in FIG. 1.

As each length of cable 16 and 20 is drawn from the housing the positionof the first connector 110 is not materially altered. Excess cable notrequired for making connections between adjacent boreholes is left inthe housing.

By mounting two coils inside the housing multiphase manufacturing stepsare made possible. The housing, with its contents, can be moved orindexed through sequential automated manufacturing processes. Thedetonator and the connectors can be tested while secured within thepackaging.

The outer sleeve is preferably pre-printed with deployment instructionsand safety information as may be stipulated by local and internationallegislation. The sleeve is kept in position, relatively to the housing,by means of the folded portion 124 which engages with a correspondingrecess 42B.

The recessed formations 42A and 42B facilitate handling of the housingfor they provide convenient handgrips.

The detonator 116 is preferably stored as is shown in FIG. 2, within theconfines of the first coil 90. This, together with the partitionedpackaging design, provides a substantial amount of separation ofdetonators which are in a plurality of detonator assemblies. Thedetonator can be removed from the housing without undue handling of thehousing.

FIGS. 12 to 14 illustrate a detonator assembly 30A, according to avariation of the invention, which bears substantial similarities to thedetonator assembly 30. Consequently, where relevant, like referencenumerals are used to designate like components.

First and second coaxially aligned coils 90 and 92 respectively, whichare slightly spaced from each other, are formed using any suitabletechnique. Each cable coil has a plurality of windings 150, 152 around acorresponding hollow core 90A, 92A, and has a circular cylindricalshape. The cable coils are linked by a cable section 100 to which aconnector 110 is crimped. An end 82 of the first coil is connected to adetonator 116 -which is positioned inside the hollow core 90A of thefirst coil. An end 98 of the second coil, accessible from the hollowcore 92A of the second coil, is connected to a connector 114 which canbe mated to the connector 110.

The coils 90 and 92 are separately wrapped in a suitable sheet material,e.g. a cling-wrap plastic material 160 and 162, and the coils are thenheld in a fixed relationship to each other by means of a confinementstructure which comprises a shrink wrapping 164 which has openings 166and 168 at opposed ends of the assembly through which the detonator 106and the connectors 110 and 114 can respectively be accessed.

FIG. 14 is similar to FIG. 1 and depicts a blasting arrangement which isestablished through the use of a plurality of the detonator assemblies30A. For the sake of convenience reference numerals which are the sameas those in FIG. 1 are used to designate like components.

The detonator assembly 30A is used in substantially the same way as thedetonator assembly 30. The wrapping 164 is cheaper than the housing 32and, apart from the access openings 166 and 168, is waterproof.

In the preceding description the cable coils 90 and 92 are linked by theintegral cable section 100. Although this is a preferred form ofconstruction it is not essential for the respective end portions of thecable coils could be interconnected through the use of a suitableconnector 110, which is also designed to engage with a connector 114.

The detonator assembly provides a means of connection between detonatorsinside the same blast hole or in sequential blast holes, by permittingsufficient cable to be withdrawn from the housing. Unused cable remainssecurely within the packaging and the likelihood of cable knots ordamage occurring is reduced.

The invention has been described with reference to the use of a singledetonator in each borehole. Similar techniques can be employed to makeconnections between two or more detonators in a single borehole, ifrequired.

1-20. (canceled)
 21. A detonator assembly which includes a first cablecoil with first and second ends, a second cable coil with third andfourth ends, a detonator connected to the first end of the first cablecoil, a first connector connected to the second end of the first cablecoil and to the third end of the second cable coil, and a secondconnector connected to the fourth end of the second cable coil andwherein a first variable length of cable, extending from the first end,can be drawn from the first cable coil without materially moving thefirst connector and a second variable length of cable, extending fromthe fourth end, can be drawn from the second cable coil withoutmaterially moving the first connector.
 22. A detonator assemblyaccording to claim 21 wherein the first cable coil is provided in theform of a first tubular roll.
 23. A detonator assembly according toclaim 22 wherein the first end is inside the first tubular roll.
 24. Adetonator assembly according to claim 21 wherein the second cable coilis in the form of a second tubular roll.
 25. A detonator assemblyaccording to claim 24 wherein the fourth end is inside the secondtubular roll.
 26. A detonator assembly according to claim 21 whereineach cable coil is at least partly enclosed in sheet material.
 27. Adetonator assembly according to claim 21 wherein the cable coils areco-axially aligned with each other.
 28. A detonator assembly accordingto claim 21 which includes confinement structure for maintaining thecable coils in a desired configuration.
 29. A detonator assemblyaccording to claim 28 wherein the confinement structure is a housingwhich is made from rigid sheet material.
 30. A detonator assemblyaccording to claim 28 wherein the confinement structure comprisesflexible sheet material.
 31. A detonator assembly according to claim 30wherein the flexible sheet material is shrunk onto the cable coils. 32.A detonator according to claim 28 wherein the first connector isaccessible without removing the confinement structure.
 33. A detonatoraccording to claim 28 wherein the confinement structure includes firstand second compartments for the first and second cable coilsrespectively.
 34. A detonator assembly according to claim 30 wherein theconfinement structure is circular cylindrical.
 35. A detonator assemblyaccording to claim 30 wherein each cable coil comprises a plurality ofwindings which are arranged in over-lying layers around a hollow coreand which form a circular cylindrical shape, with the first endextending from an innermost winding of the first cable coil, and thefourth end extending from an innermost winding of the second cable coil,the detonator assembly including confinement structure around the cablecoils.